BIOL101 Exam 3

Turner's Syndrome Symptoms:

(Female because there is no Y) ¥ Short stature ¥ swelling of the hands and feet ¥ Broad chest and widely spaced nipples ¥ Low hairline ¥ Low-set ears ¥ Reproductive sterility ¥ Increased weight, obesity ¥ Small fingernails ¥ Characteristic facial features ¥ Webbed neck

Turner's Syndrome

(X) [sometimes written as XO] • Condition that affects only females, results when one of the X chromosomes is missing.

Prophase I - Crossing Over

--Crossing over: segments of non-sister chromatids break and reattach (exchange genes) to the other non-sister chromatid on the other homologous chromosome --Causes Genetic Recombination (Variation)

Homologous Chromosomes

--Pair of chromosomes that are similar in shape and size. --Homologous pairs (tetrads) carry genes controlling the same inherited traits. --Each locus [loci] (position of a gene) is in the same position on homologues [homologous chromosomes].

The Process of Gamete Formation

-Interphase I -Meiosis I (4 Phases) *Prophase I *Metaphase I *Anaphase I *Telophase I -Meiosis II (4 phases) *Prophase II *Metaphase II *Anaphase II *Telophase II

Codominance

2 dominant alleles affect phenotype in separate, distinguishable ways **BOTH phenotypes are present

In humans, a zygote with ________________ has only one copy of a particular chromosome monosomy.

45 chromosomes

Diploid

46 chromosomes (23 pairs) **Haploid = 23 chromosomes **Haploid (sperm) + Haploid (egg) = Diploid (zygote)

In humans, a zygote with _______________ has three copies of a particular chromosome trisomy.

47 chromosomes **As humans, we typically have 46 chromosomes in a normal cell

A zygote has the ______ number of chromosomes A. Diploid B. Haploid C. Polyploid

A. Diploid

Mendel was the first to propose that allele pairs segregate from each other when gametes are formed, which is known as Mendel's law of segregation. We now know that segregation of alleles is a result of the behavior of chromosomes during meiosis. Segregation of alleles in meiosis will happen when which of the following occurs? A) Homologous chromosomes separate during meiosis I. B) Homologous chromosomes separate during meiosis II. C) Sister chromatids separate from each other during meiosis I. D) Homologous chromosomes undergo crossing over.

A) Homologous chromosomes separate during meiosis I.

List an example of a cell in your body that undergoes mitosis. How many chromosomes does that cell have?

A skin cell would undergo mitosis. A human skin cell would normally have 46 chromosomes.

Incomplete Dominance

A third (new) phenotype appears in the heterozygous condition as a blend of the dominant and recessive phenotypes. **Ex - Dominant Red (R) + Recessive White (r) = Hybrid Pink (Rr) --1 allele is not completely dominant over the other, so heterozygote (Hh) has intermediate (or mixed) phenotype between 2 alleles

Multiple Alleles

A type of codominance **More than two alleles for the trait **Ex: Human Blood type

A similarity that meiosis shares with mitosis is which of the following? A) They both undergo chromosome duplication. B) They both have two rounds of cell division. C) They both occur in somatic cells. D) They both have only one round of cell division.

A) They both undergo chromosome duplication.

How many chromosomes do human gametes (egg or sperm) have? A. 23 B. 45 C. 46 D. 47

A. 23

What would the phenotype of a heterozygous individual be if black coat color is dominant over white coat color in mice? (Assume complete dominance). A. Black (the black allele is dominant over the white so white will not show at all) B. White C. Grey D. Black with white spots

A. Black (the black allele is dominant over the white so white will not show at all)

How does crossing over increase genetic diversity? A. Crossing over increases the different combinations of genes present in a gamete. B. Crossing over allows specific genes to travel together on one chromosome. C. Crossing over increases the incidence of mutations in genes. D. Crossing over prevents the inheritance of harmful mutations.

A. Crossing over increases the different combinations of genes present in a gamete.

Determine whether each of the following cells is haploid or diploid. A. An egg B. A cell from your liver C. A zygote D. A sperm E. A cell from your heart

A. Haploid B. Diploid C. Diploid D. Haploid E. Diploid

What specifically separates during meiosis I? A. Homologous chromosomes B. Sister chromatids (divide in Meiosis II) C. The cytoplasm D. The genome

A. Homologous chromosomes

The genotype FF is known as __________________. A. Homozygous dominant B. Homozygous recessive (ff) C. Heterozygous (Ff)

A. Homozygous dominant

Match the following terms to their correct description: P generation, F1 generation, genetic cross, and Punnett square. A. The organisms that are crossed to produce the first generation of offspring B. Mating a pea plant with purple flowers with a pea plant with white flowers C. The offspring that result from mating two parents of the P generation D. A diagram for predicting offspring of a particular mating

A. P generation B. genetic cross C. F1 generation D. Punnett Square

In a cell you see 23 pairs of chromosomes (homologous chromosomes) forming a tetrad. Crossing over is occurring. What phase of meiosis is this? A. Prophase I (crossing over ONLY occurs in prophase I) B. Prophase II C. Metaphase II D. Telophase II

A. Prophase I (crossing over ONLY occurs in prophase I)

If mitosis makes somatic (body) cells, what does meiosis make? A. Sex cells B. Heart cells C. Nerve cells D. Body cells

A. Sex cells

Mitosis is a cellular process that produces A. Two genetically identical daughter cells B. Four genetically identical daughter cells C. Two similar, but not genetically identical daughter cells D. Four similar, but not genetically identical daughter cells

A. Two genetically identical daughter cells

Upon fertilization, the egg and sperm fuse to form a single cell called a(n) ________. A. Zygote C. gamete B. Embryo D. gonad

A. Zygote

During which stage of meiosis do homologous chromosomes separate? A. meiosis I B. meiosis II C. interphase D. cytokinesis

A. meiosis I

Types of Chromosomes

Autosomal & Sex

What is Cystic fibrosis?

Autosomal (nothing to do with sex determination) genetic disease inherited from the parents • Changes how your body makes mucus and sweat. ♣ Affects the lungs and digestive system ♣ Caused by a mutation in a gene • Symptoms: Mucus that's too thick or sweat that's too salty ♣ If heavy mucus clogs your lungs, it's hard to breathe. ♣ It can also block your pancreas, so you can't digest your food as well. --Blocks passageways that digestive enzymes flow through to the intestines to digest food. ~2500 babies are born with CF each year ¥ Most common fatal genetic disease in the US

Multiple forms of a gene are referred to as _________________. A) traits B) alleles C) characters D) dominant alleles

B) alleles

If a cell had 12 chromosomes at the beginning of meiosis II, how many would each daughter cell have after the completion of meiosis II (cells go from diploid to haploid in Meiosis I)? A. 6 B. 12 C. 18 D. 24

B. 12

How many chromosomes did you inherit from your father? A. 2 B. 23 C. 24 D. 46

B. 23

If a cell starts out with 86 chromosomes, how many chromosomes will there be in each cell formed at the end of meiosis II? A. 86 B. 43 C. 172 D. 21

B. 43

What is a gene? A. A malignant growth resulting from uncontrolled cell division B. A segment of DNA that controls the production of a protein C. An arrangement of chromosomes used to detect genetic abnormalities

B. A segment of DNA that controls the production of a protein

Gametes have the ______ number of chromosomes A. Diploid B. Haploid C. Polyploid

B. Haploid

Why are there two sets of phases in meiosis? A. To produce double the number of chromosomes in each gamete B. To produce half the number of chromosomes in each gamete C. To produce triple the number of chromosomes in each gamete

B. To produce half the number of chromosomes in each gamete

If short hair (L) is dominant to long hair (l), animals with LL and Ll have the same A. genotypes B. phenotypes C. alleles D. genes

B. phenotypes

A plant that produces yellow seeds is bred with a plant that produces green seeds. All of the seeds of the offspring are yellow. Which of the following explains this result? A) The yellow allele is recessive to the green allele. B) All of the offspring are homozygous for the yellow allele. C) The yellow allele is dominant to the green allele. D) Yellow is an easier color to produce.

C) The yellow allele is dominant to the green allele.

At the end of meiosis II, there are ___ cells and they are all _________. A) four; diploid B) two; haploid C) four; haploid D) two; diploid

C) four; haploid

How many chromosomes do human somatic (body) cells have? A. 23 B. 45 C. 46 (23 pairs) D. 47

C. 46 (23 pairs)

When does crossing over occur? A. Cytokinesis B. Mitosis C. Meiosis I (prophase I) D. Meiosis II

C. Meiosis I (prophase I)

What is different between two versions of the same gene? A. Their location. For example, one version might be at the end of one chromosome, while the other version is in the middle of another chromosome. B. The chromosome number they are on. For example, one version might be on chromosome 12, while the other one is on chromosome 3. C. The information they carry. For example, one version might carry the information for blue eye pigment, while the other carries the information for brown eye pigment. D. The cell they are in. For example, one might be in a liver cell, while the other is in a blood cell.

C. The information they carry. For example, one version might carry the information for blue eye pigment, while the other carries the information for brown eye pigment.

At what stage of meiosis does crossing over occur? A. metaphase I B. metaphase II C. prophase I (Meiosis I) D. prophase II

C. prophase I (Meiosis I)

A homozygous recessive genotype would look like _________. A. HH B. Ff C. rr D. AB

C. rr

What causes Cystic Fibrosis?

CF is caused by a recessive allele (mutation) **an allele that affects phenotype only if the organism has two copies of that allele --hidden by normal or dominant allele **People with normal phenotypes can still pass CF allele to offspring **They are called carriers and are heterozygous individuals. --Carriers do not have the disease, but they can pass it on to offspring.

Meiosis I

Cell division that reduces the chromosome number by one-half. --Four phases: Prophase I, Metaphase I, Anaphase I, Telophase I **46 chromosomes -> 23 chromosomes

Sexual Reproduction

Creates a diploid zygote from the fertilization of the haploid egg and haploid sperm.

____________________________________ contain the same genes at the same locations. A) Sex chromosomes B) Autosomes C) Gametes D) Homologous chromosomes

D) Homologous chromosomes

What is the phenotype of an individual who is heterozygous for dimples? A) Dd B) DD C) dd D) None of the above

D) None of the above

Mitosis creates ________________, while meiosis creates _____________________. A) haploid gametes; diploid gametes B) diploid somates; diploid gametes C) haploid somates; haploid gametes D) diploid somates; haploid gametes

D) diploid somates; haploid gametes

A skin cell is to a somate as a(n) ________ is to a gamete. A) embryo B) zygote C) brain cell D) egg

D) egg

How many chromosomes would a typical human cell have after mitosis but before cytokinesis? A. 0 B. 23 C. 46 (46 per cell but the cell has not yet divided) D. 92

D. 92

From the possibilities below, what genotype will produce blood type O? A. IBIB B. IAIB C. IAIA D. ii

D. ii

When do sister chromatids separate? A. meiosis I and meiosis II B. meiosis I and mitosis C. mitosis and cytokinesis D. meiosis II and mitosis (basically the same thing)

D. meiosis II and mitosis (basically the same thing)

What type of normal human cell contains 22 autosomes and a Y chromosome? A. egg cell B. somatic (body) cell of a female C. somatic (body) cell of a male D. sperm cell (because there are only 23 chromosomes)

D. sperm cell (because there are only 23 chromosomes)

Types of Alleles

Dominant & Recessive

List three human characters and then provide two traits for each listed character.

Eye color: hazel & blue Hair color: black & red Hairline: straight & widow's peak

True or false: A situation where a human is missing an autosome is not fatal. If false, make it a true statement.

False, it is always fatal.

True or false: At the end of meiosis I, the two cells are both diploid. If false, please explain why.

False, the two cells are haploid because homologous pairs of chromosomes separate during meiosis

Blood Type: O

Genotype: ii Can donate blood to: A, B, AB, O (universal donor) Can receive blood from: O **requires 2 recessive alleles **universal because there are no proteins on the outside of the blood cell

Sex - Linked Traits

Gene located on either of the sex chromosomes (located only on the X chromosome - mutation on the Y chromosome is exceedingly rare [very few live to childbirth if they have Y mutations]) **In addition to their role in determining sex of an organism, X and Y chromosomes have many other genes that are unrelated to sex. • Sex-linked mutations can be either dominant or recessive.

Blood Type: A

Genotype: I^AI^A or I^Ai Can donate blood to: AB, A Can receive blood from: O, A

Blood Type: AB

Genotype: I^AI^B Can donate blood to: AB Can receive blood from: A, B, AB, O (universal receiver) **has codominant alleles **Since it has two types of proteins, they can only donate to other type AB people or their body will reject the blood

Blood Type: B

Genotype: I^BI^B or I^Bi Can donate blood to: AB, B Can receive blood from: O, B

___________________ is the study of how traits are passed from generation to generation.

Heredity

Are the alleles on the homologous pair of chromosomes in the following figure homozygous or heterozygous?

Heterozygous

Types of Genotypes (all the genes we have)

Heterozygous & Homozygous

_____________ is the type of cell division that produces gametes.

Meiosis

Two cell divisions in Meiosis

Meiosis I and Meiosis II

How do we get these different versions (alleles)?

Mutations

In Labrador retrievers, black coat color is dominant to chocolate coat color. Would you need to create a Punnett square if you wanted to mate two chocolate labs? Briefly explain your answer either way.

No, because if the two labs have chocolate coats, it is because they are both homozygous recessive. Every offspring would also be homozygous recessive and have chocolate coats.

Where does Meiosis occur?

Occurs only in gonads -(testes [sperm] or ovaries [eggs]). **Meiosis in males is called spermatogenesis and produces sperm **Meiosis in females is called oogenesis and produces eggs (ovum)

Complete Dominance

Occurs when the phenotypes (physical characteristic) of the heterozygote (Hh) and dominant homozygote (HH) are identical.

Prophase II

Same as Prophase in mitosis ♣ Nuclear membrane disappears and chromosomes condense ♣ Spindle forms

Telophase II

Same as Telophase in mitosis: nuclear envelope reappears • Cytokinesis II occurs. • Four haploid daughter cells are produced. Called gametes (eggs and sperm-)

Anaphase II

Same as Anaphase in mitosis: sister chromatids separate

Metaphase II

Same as Metaphase in mitosis

_________________ is the process that results from the union of gametes from two different parents.

Sexual Reproduction

Interphase I

Similar to mitosis interphase. **Chromosomes (coiled up DNA & proteins) replicate **Each duplicated chromosome consists of two identical sister chromatids attached at their centromeres

At the start of Meiosis vs. At the end of Meiosis

Start: there are 46 chromosomes (23 pairs) in the parent cell End: there are 23 chromosomes in each of four new cells that were produced

Meiosis

The form of cell division by which sex cells produce gametes, with half the number of chromosomes, are produced.

A cell biologist observes a cell under a microscope and determines that the cell contains nine chromosomes. Is this cell diploid or haploid? Briefly explain your answer.

The cell is haploid because, assuming homologous pairs of chromosomes, a haploid cell would have an odd number of chromosomes.

Each row and column in a Punnett square represents a gamete that each parent can produce. Briefly explain why each gamete has only one allele in it.

The gametes will have only one allele because they will be haploid, and haploid cells only have one of each chromosome.

In Labrador retrievers, black coat color is dominant to chocolate coat color. A geneticist performs a genetic cross where she mates a chocolate Labrador retriever with a black lab. The F1 offspring show a 50/50 mix of chocolate to black labs. What was the genotype of the black lab in the P generation? What kind of genetic cross is this called?

The genotype of the black lab in the P generation was Bb. This was a test cross

A normal human egg or sperm has 23 chromosomes, which is exactly one half what a somatic cell has. Briefly explain what would happen every generation if gametes were actually diploid.

The number of chromosomes would double from generation to generation.

Nondisjunction in Autosomal (doesn't determine sex) Chromosomes: Down Syndrome

This condition is called trisomy 21

Briefly explain why only chromosomes of a homologous pair can have their alleles referred to as homozygous or heterozygous.

This is because only homologous chromosomes would have the same genes at the same physical locations on those chromosomes. Otherwise, the alleles of different genes would have no relationship.

Can a karyotype be used to determine the gender of an individual? Briefly explain your answer either way. Hint - Look at the figure at the bottom of page 89 of your textbook.

Yes, a karyotype can be used to determine gender, because you can use a karyotype to see chromosomes and place them into their homologous pairs.

What do you know for sure about the genotype of any organism whose phenotype is the recessive trait? Think of pea plants with white flowers.

You would know that the pea plant has to be homozygous recessive for the genotype.

Autosomal

all chromosomes in a person's cells except for those that determine the sex. 22 pairs

Dominant Alleles

allele that determines what an organism looks like (capital letter) Example: Cystic Fibrosis: FF, Ff **Allele that prevents the other allele from "showing" - dominant

Sex - Linked Traits (Mothers)

can pass sex-linked alleles to BOTH sons and daughters o XX (Mother) XX (daughter) **mom has options as to what she's going to pass down because both of her chromosomes are sex-linked o XX (Mother) XY (son)

Yellow is to pea-seed color as ____________________ is to coat color in Labradors

chocolate

Sex

chromosomes that determine sex. 1 pair **XX: female, XY: male

Mitosis is to a somate as meiosis is to a(n) _____________________

gamete

Purple-flower color is to pea-plant-flower color as red hair is to _______________________

human hair color

A(n) ________________ is a mating that examines one character between two parental organisms.

monohybrid cross

Prophase I

o Chromosomes condense. o Synapsis (coming together) occurs - Homologous chromosomes (chromosome pairs) come together to form a tetrad. o Tetrad is two chromosomes or four chromatids (sister and non-sister chromatids).

Sex - Linked Traits (Fathers)

pass sex-linked alleles to ALL their daughters but NONE to their sons o XY (Father) XX (daughter) **father will have to donate X chromosome to have a daughter o XY (Father) XY (son) **father will always pass Y chromosome to son, not the sex-linked, or X chromosome

Recessive Alleles

phenotype that is expressed only if two copies of the allele are inherited. (lower case letter) Example: Cystic Fibrosis, ff **Allele that does NOT "show" even though it is present - recessive Symbol - Dominant gene - upper case letter - T Recessive gene - lower case letter - t **Must have 2 recessive alleles for a recessive trait to "show"

Gametes

sperm or egg cells

Punnett squares

table that predicts possible outcomes of a cross (mating between two parents)

Nondisjunction can also affect the sex chromosomes when...

there can be too many or too few X or Y chromosomes (XX- normal female, XY-normal male)

Heterozygous

when an organism has two different alleles for a gene, Ff

Homozygous

when an organism has two identical alleles for a gene, FF or ff

Klinefelter's Syndrome

¥ An extra X chromosomes: XXY (because of the Y chromosome, it's a male individual) ¥ X chromosomes determine all sorts of biological developments for females - when said chromosomes outshine Y, individuals will have more female characteristics ¥ First sex chromosome abnormality to be reported

Cystic fibrosis (CF)

¥ Caused by a single gene mutation ¥ Allele of the CFTR gene ¥ CFTR gene codes transmembrane regulator protein ¥ Moves chloride in and out of cells Ð Determines whether water can enter or leave the cell

Non-Sister Chromatids

¥ Homologous chromosomes contain DNA that codes for the same genes, but different versions of those genes ¥ Genes occur at the same loci (location on a chromosomes) **gene (& gene variation)- blood type (both chromosomes would have the gene, but the "versions" would be the types of blood that you actually have)

What happens when meiosis goes wrong?

¥ Nondisjunction_- failure of chromosomes to separate and segregate (group) into daughter cells ¥ May occur during meiosis I or meiosis II ¥ Produces gametes (sperm or egg) that have too many or too few chromosomes

Prophase I (pt. 2)

¥ Nuclear membrane (envelope) disappears & spindle [what moves the chromosomes] forms ¥ Chromosomes coil & synapsis (pairing) occurs ¥ Tetrads form & crossing over (only in prophase) occurs

Down Syndrome -- Characteristic facial features

¥ Round face, flattened nose bridge ¥ Small, irregular teeth ¥ Short stature, heart defects

Metaphase I

¥ Tetrads (pairs of homologous chromosomes) align on the equator (middle). ¥ Independent assortment occurs - chromosomes separate randomly causing genetic recombination (variation)

Mutations

• A change in a piece of the DNA (gene), often happens when DNA is being copied o Results in a different variation of the gene, called alleles • Mutations create new alleles

Klinefelter's Syndrome Symptoms:

• Appear normal until puberty • Significantly reduced IQ • Language impairment • Taller than normal • Poor muscle tone • Breast development • Low levels of Testosterone and small testicles / Infertile

Telophase I

• Each pole now has haploid (1n) set of chromosomes. • Cytokinesis occurs and two haploid daughter cells are formed. (1 parent, 2 daughter cells)

Anaphase I

• Homologous chromosomes separate and move towards the poles. • Sister chromatids remain attached at their centromeres.

Meiosis II

• Interphase II is very short • No DNA Replication • Remember: Meiosis II is similar to mitosis

Genetic Inheritance: How do we inherit traits?

• Traits are determined by the genes on the chromosomes. A gene is a segment of DNA that determines a trait. • Examples of Genes: o Hair color, Eye color, hair texture, Skin Color

What are the different variations (versions) that we see in genes?

♣ More than one type of hair texture (gene) o Wavy, Straight, Curly ♣ These versions are called alleles